How to deal with condensation in an RV

If you are an RVer in the north and, like us, live year round in four seasons, you have no doubt found out that condensation, especially in the winter, is something that can’t really be avoided. In this article we will explain what causes condensation, then help you figure out which areas in your RV are prone to condensation. We will also give you some way that you can use to reduce the humidity in your RV to help remove condensation.

As with most things when it comes to owning an RV and/or living in an RV full time or even part time, there are ways to prepare for the inevitability of condensation. Even if your RV is fully winterized and parked during the off season, condensation should still be a concern.

Condensation occurs most when cold air and warm air meet.  For example, when it’s cold outside and warm, moist air produced inside your RV hits cooler interior walls and windows.  But condensation can also happen in other ways. Such as when it’s hot and humid outside and air conditioned inside, or in early spring when your RV is still cold inside from being in storage all winter.

In either case, there are ways to address the issues and reduce the condensation to a point where it won’t cause issues with your RV.  These issues can include things like mold, which you definitely don’t want to develop in your small space.

In order to reduce condensation, you first need to find the “weak spots” in your RV. These are the places where condensation forms. Next, you need to come up with a plan to deal with those “weak spots”.

1. Weak Spot #1 – drafty and/or single pane windows. In most RVs the glass is single pane. This is because most RVs are designed for spring, summer and fall use and not often built for 4 season use.
2. Weak Spot #1 – faulty or non-existent seals around doors. With some older RVs you may have a door that doesn’t seal fully. Most doors are also very thin, which makes them prone to be colder than many of your walls.
3. Weak Spot #3 – areas of your RV that don’t normally get heat (which are located on the outside walls). This can include places like the voids behind drawers and cupboards, and the insides of closets.
4. Weak Spot #4 – any other area exposed to cooler temperatures outside. This would include the windshield on motorhomes, roof vents, and skylights, and even the undercarriage of your RV.

The best way to reduce condensation in your RV is to reduce the source of the condensation. This is done by doing 2 things:

1. Remove moisture in the air, and
2. Fix areas where condensation is prone to occuring.

As you may have guessed, the best way to reduce condensation in your RV is to remove the moisture in the air. This can be done various ways, which we’ll show you below.

In addition to this, to make sure the condensation doesn’t reoccur we will show you things you can do to to your RV to help lower the chance of it returning.

The best way to make sure your RV doesn’t get overrun by condensation is to prepare for it. That means removing those “triggers” which allow condensation in the first place.

Whether your RV is winterized and parked for the season or you are living in it full time, these are things you should do.

First, is to make sure your RV is as air tight as you can make it. Make sure windows are closed, doors are closed tight and if you have storm windows, install them. Perform an inspection of your RV inside and out and look for places where cold air may enter (such as around your water, sewer and electrical hookups).

Also look for any voids which may allow cold air to become trapped. Be sure to look inside any of your basement storage compartments in your RV as well. That is because these can be subject to condensation by having warmer air from the floor migrate down into the cooler storage spaces.

Practical Example:

For example, in our Class A there is a void behind the 3 cabinets we have above the drivers and passengers seats. Originally the middle cabinet was where the old tube TV was installed, while the cabinet above the passenger seat contained the signal switch, antenna booster and other electronic gadgets.

The compartment above the driver’s seat is mostly empty. Both the compartments above the driver and passenger seats are fully enclosed and even have spray foam installed around them, so they are free from condensation issues, but the center cabinet is open to the plastic header where the marker lights above the windshield are located. Obviously it is built this way so you have access to, and can easily change the bulbs, but in our RV this is an area prone to condensation. We addressed this by first removing as much moisture as we could that was already there (and there was a lot) and then adding a moisture absorbing product. I then enclosed the middle compartment with reflectix to help reduce the amount of air moving from inside the cabin to the void.

When your RV is winterized and parked, the best method is to use something like Dri-Z-Air throughout your RV. This is a product that uses a chemical reaction to draw out moisture which then deposits the water it collects into a reservoir. Dri-Z-Air on its own is not enough however. You do need some sort of receptacle where the water is deposited.

There are many options here, so don’t feel that you HAVE to use only Dri-Z-air. For example, we found small disposable units in our local dollar store. They have moisture removal product in the top of a disposable container that collects the water down below. You just have to remove the lid and pull off the plastic that protects the absorbent material and then place the entire unit where you want it.

In our case we bought 10 or 15 of these and placed them throughout the basement storage, as well as in a few closets and other areas that we felt would be prone to condensation. And I have to tell you, we were right. In our bedroom closets, which are on the back of the RV, 3 of the 4 containers filled up in a couple months. We’ve already replaced many of them.

A very quick way to remove humidity from your RV is to open a window or turn on a vent. This is particularly useful when cooking or showering as many roof vents can move a lot of air in a short period of time. We’ve lowered our internal humidity by 5-10% in just a matter of minutes by opening a vent and turning the fan in it on high for a few minutes.

If you live in your RV year round this may be something you want to consider. Much like the heat shrink clear plastic window kits you’d use in your sticks and bricks home. You can use the same window kits in your RV. Best of all, because an RV usually has fewer windows, the cost of such kits is reasonable. If you live in a motorhome, don’t forget to do your windshield and side windows as well, as these can be massive sources of condensation. The same goes for skylights.

If you have roof vents you won’t be using often, you can also use these kits there.

Some RVers like to use flexible Reflectix on their windows, doors and other cold areas. This is a great option for insulating – especially inside – but you have to be careful to seal around it really well. This is because moisture can become trapped on the exterior wall or window behind the reflectix. This will usually result in the growth of mold where the warm humid air meets the colder surface, like your exterior wall. Reflectix is also a good way to skirt your RV (see below)

Some full-timers, us included, prefer to use electric heaters over our furnace to keep warm. We set our furnace at a lower temperature and use it as a backup heat source. We do this partly because electricity is cheaper where we are, but also because propane heat actually puts moisture into the air.

That being said, with some RVs running the furnace is required to keep not only the underbelly of the RV warmer, but also ensures plumbing doesn’t freeze in colder climates.

If you do run electric heaters, we suggest ones with fans so that they can move the warm air further in your RV and help dry things out. A well placed electric heater can reduce moisture on your interior of your walls resulting in lower humidity.

Even a small electric oscillating fan would be better than nothing as it helps move air around, reducing moisture on surfaces.

If you are like us and are parked in a permanent spot, you should consider skirting your RV. This year we are using 3 inch foam panels to skirt our RV but last year we used Reflectix. Both work well.

You can also find people to custom make you skirting which can be added or removed using velcro, snaps or other methods. The method you use to skirt doesn’t matter too much, as long as you are fully skirted and there are no gaps in the skirting to allow air in underneath your RV.

Along with skirting, if your RV has slides you should insulate those as well – top, bottom and (optionally) sides. In our case we have 1 large slide. I put the same foam that I used for skirting on the top and bottom and used reflectix for the sides.

This has made a big difference for us this year, as last year I didn’t insulate the slide and we could feel the cold air coming in around the slide all winter. This year there is none.

We found that when it gets really cold (-10 celsius or below) it really helps to open doors and drawers. While this does increase the presence of cooler air into your RV, it also helps air get back into those cooler areas to reduce moisture. You may find in particular that clothes closets on exterior walls are one of the worst areas for condensation, as we did last year.

Opening doors and drawers can also help make sure the plumbing inside your RV doesn’t freeze, especially if you rarely use the propane furnace and opt to run electric heaters like us.

In some cases, before it gets too cold or hot, it would be a good idea to use reflectix inside these spaces. Again, make sure it is well sealed by taping all 4 sites with a good tape so that moisture can’t get behind it and allow mold to form.

We found that when it gets really cold (-10 celsius or below) it really helps to open doors and drawers. While this does increase the presence of cooler air into your RV, it also helps air get back into those cooler areas to reduce moisture. You may find in particular that clothes closets on exterior walls are one of the worst areas for condensation, as we did last year.

Opening doors and drawers can also help make sure the plumbing inside your RV doesn’t freeze, especially if you rarely use the propane furnace and opt to run electric heaters like us.

In some cases, before it gets too cold or hot, it would be a good idea to use reflectix inside these spaces. Again, make sure it is well sealed by taping all 4 sites with a good tape so that moisture can’t get behind it and allow mold to form.

Even if you are a seasoned RVer this is something you may not consider. Mattresses, cushions and furniture against exterior walls are usually pressed right up against them. Therefore air can’t circulate behind them. But moisture always somehow finds a way. Moisture can get behind these things which then allows mold to form.

So during the day consider pulling your mattresses away from walls, particularly when it gets quite cold out. Just a couple inches is needed to allow air to flow freely. Similarly, pull cushions away from walls.

If you have fabric blinds or curtains you may also want to open them occasionally to allow air to flow around your window to reduce moisture.

This one applies more to motorhome owners. On your dashboard or other flat surfaces, consider laying down towels or some other soft fabric to absorb water. You may find condensation form on the windshield and then roll down and collect on the dash. Simply laying towels out will help absorb that moisture and reduce condensation. Be sure to change out the towels regularly so they don’t start to develop mold.

No matter how prepared you think you are, you may still find moisture collecting in places. In this case, just grab a rag and wipe it off. You definitely don’t want moisture to sit and accumulate because that will lead to mold.

We recently purchased a new weather station at Costco that has helped as well. Itnot only shows us the interior and exterior temperatures, and the wind speed, but it shows the humidity inside and out. Once we figured out a comfortable humidity level we are able to check it to make sure we are in our comfort zone.

If we get above the comfort zone, we turn on a fan or crank up an electric heater a little bit and that helps lower the humidity in our RV. It also gives us the barometric pressure so that we can start to figure out when the weather is changing. This helps us plan for potential future humidity such as snow or rain and adjust our living based on that. For example if the temperature is going to drop, we know it’s going to get dryer outside which means condensation inside could become an issue. Similarly, a humid day outside, such as a rainstorm, raises the humidity (and chance of condensation) inside.

So you’ve followed some of the tips we’ve mentioned above, but you’ve still got areas that have developed mold. Now what?

Well you could mix yourself up a mixture of water and bleach (10 parts water to 1 part bleach) and wipe the areas affected. Be careful to test a small surface though to ensure the bleach doesn’t harm the surface.

There are also different chemicals you can get which are safe enough to use that help remove mold. Many of these also have mold inhibitor in them, so once the mold is removed they help to make sure the moldit doesn’t come back.

We hope that you are able to use a few of these tips we’ve provided. While we’ve found it is almost impossible to remove all the condensation from your RV all the time, especially when you live in it full time, there are ways to greatly minimize it.

The first step is to inspect your RV and try to figure out the places where condensation can form and then figure out the best way to deal with it, whether that is a moisture removal product like Dri-Z-Air, better insulation in spots, or just a small electric heater or fan.

Of course the more you can do, such as skirting your undercarriage, insulating slides, insulating windows and doors, and addressing voids, all help as well. By doing these things before humidity becomes an issue, you will reduce future condensation and ultimately the development of mold in your RV.